Harcode libtcl version to be that of the default tclsh.

--- a/configure
+++ b/configure
@@ -98,7 +98,7 @@
 fi
 if [ -n $USE_TCL ]
 then
-	LIBPOSTFIX=`ls -1 /usr/local/lib/ /usr/lib | grep 'libtcl[0-9]' | grep so | sed -e 's/\.so.*//g' -e 's/libtcl//g' | sort -r | head -1`
+	LIBPOSTFIX=`echo puts \\$tcl_version | $TCLSH -`
 	TCL_LIB="-ltcl${LIBPOSTFIX} -lm -lpthread"
 fi
 
